Cold therapy device with thermo-mechanical mixing valve

ABSTRACT

A cold therapy unit incorporates a cold reservoir containing a cold treatment fluid, typically water with ice and a treatment pad with an inlet line and an outlet line. A thermo-mechanical mixing valve receives treatment fluid from the reservoir and warmer fluid from the pad in a ratio that results in treatment fluid of the desired temperature. A pump delivers that treatment fluid to the inlet line on the pad. A portion of the treatment fluid exiting the pad through an outlet line will return to the reservoir and a portion to the mixing valve as required to maintain a predetermined temperature in the mixing valve.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates generally to cold therapy, andspecifically to improving the safety and effectiveness of a cold therapyunit which reduces pain and swelling at an injury site of a patient.

2. Description of Related Art

Cold therapy or cryotherapy (e.g., ice) is used to reduce pain andswelling, otherwise known as edema formation, from an acute injury orpost-surgery site. The therapy is especially useful for injuries such assprains, strains, pulled muscles, and pulled ligaments during sports andother activities. Cold therapy is also often recommended by orthopedicsurgeons following surgery, as ice is one of the principles of Rest,Ice, Compression, and Elevation (RICE) therapy.

The ice principle, known as cryotherapy, is the use of cold or ice tolower the temperature of the injured tissue, which reduces the tissue'smetabolic rate and helps the tissue survive the period following theinjury. In a therapeutic setting, cryotherapy has become one of the mostcommon treatments in orthopedic medicine.

Alternatives to ice include cold wraps such as re-freezable gel packs,which are less messy and reusable. Another popular alternative isportable cold therapy units, which are an effective and convenientalternative to icing, as the cold therapy unit circulates ice waterthrough a treatment pad wrapped around an injury or surgery site of thepatient to reduce pain and swelling. Cold therapy unit are oftenprescribed by doctors or selected by patients after surgery for use intheir home.

According to the medical community's guidelines, the length of time thatcold can be applied to an injury or wound site depends on thetemperature of the treatment medium. For example, ice, which will have asurface temperature of 32 degrees F., should generally be limited to amaximum of 15-20 minutes at a time and no more frequently then every twohours. Exceeding these established limitations puts the patient at riskfor further injury. For example, exceeding the 20 minute treatmentlimitation can cause frostbite or other damage to skin, tissue, andnerves. However a cold therapy unit, with a treatment pad having asurface temperature greater than 45 degrees F., can be appliedcontinuously for as long as needed to reduce pain and swelling.

The portable cold therapy units existing in the prior art consist of areservoir which hold ice and water, a pump to circulate the water and atreatment pad through which the water is circulated. All of the unitsthat are intended for continuous use, (greater than 20 minutes), rely onbody heat from the patient to warm the water from just above freezing toa safe level. This is typically done by controlling how fast the waterflows through the pad, typically about 4 oz. per minute. Unfortunatelythere are many variables other than flow rate that effect the resultingtemperature of the treatment water such as the size of the treatmentpad, the amount of blood circulation the patient has at the treatmentsite and the location of the treatment site on the patient. For examplean ankle typically has poor circulation while a shoulder has very goodcirculation. Also an ankle treatment pad is typically much smaller thana shoulder pad therefor the water would remain in the ankle pad for avery short time not allowing much time to warm up while it would remainin the shoulder pad much longer therefor warming to a much greaterextent. The result is that the ankle is exposed to temperatures lowerthan what are safe and the shoulder doesn't see low enough temperaturesto help much in the treatment.

The manufacturers of prior art devices deal with this issue in a coupleof ways. One way is to put a thermometer in the line returning from thetreatment pad to the reservoir and provide controls for the patient ormedical practitioner to control the flow rate of the treatment fluid sothat the desired temperature can be maintained. This method has somemajor drawbacks. One drawback is that the heath care practitioner aswell as the patient need to fully understand the proper use of thedevice as well as the risks if not used according to directions.Unfortunately, the patient often does not read through the instructionsand warnings and sometimes concludes that if a little is good a lot isbetter which often results in serious skin or nerve damage. Since thetreatment area is numb from the cold the patient does not feel any painfrom the damage that is occurring.

Another drawback to manually controlling temperature is that itsometimes results in ineffective treatment. This is because one of themajor influences on the amount of heat that is transferred from the bodyto the treatment pad is the thickness and number of layers of dressingbetween the treatment pad and the skin. What happens is that a lot ofdressing equals a lot of insulation resulting in little heat transferwhich results in the thermometer showing that the water is too cold. Thepatient, according to the instructions, would decrease the flowresulting in a warmer treatment pad and thermometer reading. With thatmuch insulation, in order to get enough heat transfer for the treatmentto be affective, the patient would actually need to increase the flowrate rather than decrease resulting in a cooler treatment pad.

Another way that manufacturers of prior art cold therapy units deal withthe problem of different treatment sites and different sizes treatmentpads having different heat transfer rates, is by having a differentfixed flow rate for each type of treatment pad. For example, an anklepad might have a flow rate one quarter of that of a shoulder pad. Whilethis method is safer than the manual control method, since the patientor medical practitioner cannot adjust the flow rate, it still does notaddress the issue of patients having differing blood circulation at anygiven treatment site due to factors such as age, health, smoking, priorsurgeries at that location, etc.

There is another major problem with all of prior art portable units thatrely on the water warming from just above freezing to a safe level in asingle pass through the pad. The water enters the inlet port of the padat just above freezing, travels an arduous path around barriers thatprevent the water from shortcutting from the inlet directly to theoutlet and then the water exits the outlet port at approximately 50degrees F. What this means is that the inlet quadrant of the pad will beclose to freezing while the outlet quadrant will be about 15 degreeswarmer. This could result in skin or nerve damage localized at the inletquadrant of the pad.

Many of the injuries such as skin necrosis, blistering and nerve damage,observed in patients using cold therapy units, are also observed inpatients who did not use cold therapy. This and the fact that there isno way to determine what temperature the treatment site experienced,makes it very difficult if not impossible to determine the exact causeof the injury. This confusion has led to each manufacturer spendingmillions of dollars each year between litigation and injury compensationfor cases that may or may not been a result of their product.

It is therefore advantageous to have a portable cold therapy unit thatdelivers a treatment fluid to a treatment pad entering the pad atconsistent and safe temperature. It is also desirable that the treatmentfluid circulates at a relatively high flow rate so that the temperatureof the fluid exiting the pad is only slightly warmer than the fluidentering the pad. Such a unit would not be subject to miss-adjustment,cold spots on the pad, and in the event of litigation, testing of theunit to determine if it was maintaining a safe temperature is moreeasily accomplished.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide a cold therapy unitincorporating a cold reservoir containing a cold treatment fluid,typically water with ice and a treatment pad with an inlet line and anoutlet line. A thermo-mechanical mixing valve receives treatment fluidfrom the reservoir and warmer fluid from the pad in a ratio that resultsin treatment fluid of the desired temperature. A pump delivers thattreatment fluid to the inlet line on the pad. A portion of the treatmentfluid exiting the pad through an outlet line will return to thereservoir and a portion to the mixing valve as required to maintain apredetermined temperature in the mixing valve.

In one embodiment of the present invention the mixing valve employs asealed chamber with two inlet ports on opposite sides of the chamber,the first inlet port receiving cold fluid from the reservoir and thesecond inlet port receiving warmer fluid from the outlet line of thetreatment pad. A bimetal strip reactive by bending in accordance withexposure temperature is oriented in the chamber to block off a first oneof the two inlet ports when the temperature of the fluid in the chamberis below a predetermined lower threshold or the second one of the twoinlet ports when the treatment fluid in the chamber is above apredetermined upper threshold. Adjustment screws calibrate thetemperature at which the fluid in the chamber is maintained.

In another embodiment of the present invention the bimetal mixing valveemploys a sealed chamber with two inlet ports on opposite sides of thechamber, the first inlet port receiving cold fluid from the reservoirand the second inlet port receiving warmer fluid from the outlet line ofthe treatment pad. A dual ended tapered needle valve is adapted for oneend to be received in each of the inlet ports to gradually increase ordecrease the flow of fluid as the needle valve is retracted from orinserted into each of the ports. A bimetal strip which is reactive inaccordance with exposure temperature is oriented in the chamber to acton the dual ended needle valve causing the respective ends to beinserted or retracted from each of the ports depending on thetemperature of the fluid in the chamber causing a restriction of flow inthe first inlet port when the fluid in the chamber is below apredetermined threshold temperature or in the second inlet port when thetreatment fluid in the chamber is above a predetermined thresholdtemperature. Adjustment screws are provided to calibrate the temperatureat which the fluid in the chamber is maintained.

In another embodiment of the present invention the mixing valve employsa sealed chamber with two inlet ports on opposite sides of the chamber.A first inlet port receives cold fluid from the reservoir and a secondinlet port receives warmer fluid from the outlet line of the treatmentpad. A bimetal coil which is reactive by winding or unwinding inaccordance with exposure temperature is oriented in the chamber to blockoff the first inlet port when the fluid in the chamber is below apredetermined threshold temperature or the second inlet port when thetreatment fluid in the chamber is above a predetermined thresholdtemperature. An adjustment screw at the center of the bimetal coil isemployed to calibrate the temperature at which the fluid in the chamberis maintained.

In another embodiment of the present invention the bimetal mixing valveemploys a sealed chamber with two inlet ports on opposite sides of thechamber, a first inlet port receiving cold fluid from the reservoir anda second inlet port receiving warmer fluid from the outlet line of thetreatment pad. A dual ended tapered needle valve is adapted for one endto be received in each of the inlet ports to gradually increase ordecrease the flow of fluid as the needle valve is retracted from orinserted into each of the ports. A bimetal coil which is reactive bywinding or unwinding in accordance with exposure temperature is orientedin the chamber to act on the dual ended needle valve causing therespective ends to be inserted or retracted from each of the portsdepending on the temperature of the fluid in the chamber causing arestriction of flow in the first inlet port when the fluid in thechamber is below a predetermined threshold temperature or in the secondinlet port when the treatment fluid in the chamber is above apredetermined threshold temperature. An adjustment screw at the centerof the bimetal coil is employed to calibrate the temperature at whichthe fluid in the chamber is maintained.

The features, functions, and advantages that have been discussed can beachieved independently in various embodiments of the present disclosureor may be combined in yet other embodiments further details of which canbe seen with reference to the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic representation of the elements of an exemplaryembodiment;

FIG. 1B is a schematic representation of the elements of a secondexemplary embodiment;

FIG. 2A is a section view of a first example bimetal valve for use inthe exemplary embodiments in a first position;

FIG. 2B is a section view of the first example bimetal valve for use inthe exemplary embodiments in a second position;

FIG. 3A is a section view of a second example bimetal valve for use inthe exemplary embodiments in a first position;

FIG. 3B is a section view of the second example bimetal valve for use inthe exemplary embodiments in a second position;

FIG. 4A is a section view of a third example bimetal valve for use inthe exemplary embodiments in a first position;

FIG. 4B is a section view of the third example bimetal valve for use inthe exemplary embodiments in a second position;

FIG. 5A is a section view of a fourth example bimetal valve for use inthe exemplary embodiments in a first position;

FIG. 5B is a section view of the fourth example bimetal valve for use inthe exemplary embodiments in a second position;

FIG. 6A is a section view of an alternative pressure valve for use inthe exemplary embodiments in a first position;

FIG. 6B is a section view of the pressure valve for use in the exemplaryembodiments in a second position;

FIG. 7A is a section view of a second example of the pressure valve foruse in the exemplary embodiments in a first position;

FIG. 7B is a section view of the second example pressure valve for usein the exemplary embodiments in a second position; and,

FIG. 8 is a flow chart of a method for providing cooled water to atherapy pad employing the embodiment disclosed.

DETAILED DESCRIPTION

Embodiments disclosed herein provide a novel method and apparatus formaintaining a safe temperature in ice water cooled cold therapy padsusing a thermo-mechanical valve for flow mixing of pumped water to thepad by receiving return flow from the pad and a cold reservoir with icewater supply. In one embodiment the return flow from the pad is routedthrough a holding reservoir before being routed to the thermo-mechanicalvalve.

Referring to the drawings, FIG. 1A shows a first exemplary embodiment ofthe elements of the system. Water is provided through a pump 10 enteringa pad 12 through an inlet line 14. The flow of water is much faster thanprior art cold therapy designs so that water entering the pad 12 isclose to the same temperature as the water leaving the pad at outletline 16. The pump 10 pulls water through a thermo-mechanical mixingvalve 18, to be described in greater detail subsequently, having a firstinput port 20 and a second inlet port 22 with the pump connected to anoutlet port 23. The first inlet port 20 receives water that hascirculated through the pad 12 and exited in outlet line 16. The secondinlet port 22 of the thermo-mechanical valve receives water from areservoir 24 through a cold conduit 26. The reservoir contains a coldfluid, typically ice water or other cooled or refrigerated fluid, toprovide the desired cooling to the pad 12. For description of theembodiments herein water will be the example fluid.

In the first embodiment, the connection between the first input port andoutlet line 16 is direct through first bifurcated line 28 a and a secondbifurcated line 28 b is provided to recirculate water to the reservoir24 for specific flow conditions to be described subsequently. In asecond embodiment shown in FIG. 1B, the reservoir 24 incorporates aholding reservoir 30 which receives returning water from the outlet line16 and a cold reservoir 32. A warm conduit 34 replaces the bifurcatedlines 28 a and 28 b to provide water from the holding reservoir to thefirst inlet port 20. The cold reservoir 32 is provided for holding theice water and is connected to second inlet port 22 in thethermo-mechanical mixing valve through cold conduit 26. A leveling port36 may be employed to equilibrate the water levels between the holdingreservoir 30 and cold reservoir 32.

Initially when the pad 12 is first applied to a patient and the pump 10is turned on, the water pumped through the thermo-mechanical mixingvalve 18 will be drawn from the cold reservoir 32 and into the pad whichwill cool to a little above freezing (or the refrigerated temperature ofthe water in the cold reservoir). Because the water is below a lowertemperature threshold, the thermo-mechanical mixing valve willsubstantially close off the second inlet port 22 receiving the icedwater and only recirculate the water from the pad outlet line 16,directly from the pad outlet line for the first embodiment or from theholding reservoir 30 for the second embodiment, through inlet port 20and through the pump 10 to the pad 12 until the water reaches thepredetermined safe temperature. At that point the thermo-mechanicalmixing valve 18 will adjust to allow inflow through cold conduit 26 tothe second inlet port 22 and allow some iced water to enter the systemto maintain that preset temperature. With a large pad such as a shoulderpad, the unit may have a hard time keeping up with the amount of heatthe body is adding to the system and the thermo-mechanical mixing valvemay shift to close the first inlet port 20 upon reaching a highthreshold temperature resulting in a higher percentage of iced waterflowing through the pad 12. In any case, no matter what size pad, whereit is placed on the body, or the health of the patient's circulation,the water being fed to the pad 12 will always be adjusted automaticallyto remain in a safe range.

The thermo-mechanical mixing valve 18 operates automatically for watertemperature adjustment. Water flowing through the valve is in contactwith an adjustment element which is reactive to the temperature to whichit is exposed and thus alters shape based on the temperature of thewater. In a first example a bimetal valve 18 a may be employed as thethermo-mechanical valve by the embodiments disclosed herein. FIG. 2Ashows a sealed chamber 40 with the two inlet ports on opposite sides ofthe chamber, the second inlet port 22 receiving cold fluid from thereservoir and the first inlet port 20 receiving warmer fluid from theoutlet port of the treatment pad. A bimetal strip 42 reactive by bendingin accordance with exposure temperature is oriented in the chamber toblock off the second inlet port 22, as shown in FIG. 2A, when thetemperature of the fluid in the chamber is below a predetermined lowerthreshold or the first inlet port 20, as shown in FIG. 2B, when thetreatment fluid in the chamber is above a predetermined upper threshold.Adjustment screws 44 calibrate the temperature at which the fluid in thechamber is maintained. The outlet port 23 delivers the mixed treatmentfluid from the chamber 40 though the pump 10 and on to the inlet line 14of the treatment pad 12. The bimetal strip will typically be made ofcopper on one surface and stainless steel on the other. In an exemplaryembodiment, a bimetal strip of about 2.5″ in length and 0.040 inches inthickness is employed. Most of the time during operation neither portwill be closed completely. The thermo-mechanical mixing valve willtypically find an equilibrium where each of the ports is delivering theproper percentage to maintain the correct temperature. Typically duringthe operation of the unit, there are only two times when the valve willbe at either of the two extremes. The first is at start up when there isno water coming back from the pad. What will happen is the valve willclose the ice water inlet, since the water will be near freezing, whichwill cause water to be drawn from the reservoir backwards up the returntube and into the mixing valve through the return inlet port. Once thepad is full and water is returning the valve will operate as intended.The only other time the valve will be at an extreme is when the ice inthe reservoir melts and the mixing valve will pull only from thereservoir.

Greater control of the flow rates of water entering the sealed chamberof the bimetal valve can be accomplished as shown in FIG. 3A where adual ended tapered needle valve 46 is adapted for a first end 48 a to bereceived in in the first inlet port 20 and a second end 48 b to bereceived in the second inlet port 22 to gradually increase or decreasethe flow of fluid as the needle valve is retracted from or inserted intoeach of the ports. The bimetal strip 42 is oriented in the chamber andattached to the dual ended tapered needle valve to act on the dual endedneedle valve causing the respective ends to be inserted or retractedfrom each of the ports depending on the temperature of the fluid in thechamber, causing a restriction of flow in the second inlet port 22, asshown in FIG. 3A, when the fluid in the chamber is below a predeterminedlower threshold temperature or in the first inlet port 20, as shown inFIG. 3B, when the treatment fluid in the chamber is above apredetermined upper threshold temperature. Flexing of the bimetal strip42 across the range from one extremity of motion to the oppositeextremity of motion reactive to the temperatures between the lower andupper thresholds allows smooth control of flow mixing between the firstand second inlet ports. Sizing of the pump, inlet and outlet ports andlines of the system are desirable for a flow of about 8 oz/min.

Alternatively, as shown in FIG. 4A, the mixing valve 18 b employs thesealed chamber 50, which may be substantially circular, connected to thetwo inlet ports on opposite sides of the chamber and a bimetal coil 52which is reactive by winding or unwinding in accordance with exposuretemperature is oriented in the chamber to block off the second inletport 22 with an extending tang 54, as shown in FIG. 4A, when the fluidin the chamber is below a predetermined lower threshold temperature orthe first inlet port 20, as shown in FIG. 4B, when the treatment fluidin the chamber is above a predetermined upper threshold temperature. Anadjustment screw 56 at the center of the bimetal coil is employed tocalibrate the temperature at which the fluid in the chamber ismaintained. In an exemplary embodiment, a bimetal coil of 1.25″diameter, 0.35″ width and 0.040″ thickness is employed.

As with the bimetal strip, greater control of flow can be achieved withthe bimetal coil 52 as shown in FIG. 5A where a dual ended taperedneedle valve 57 is connected to the tang 54 and adapted for a first end58 a to be received in in the first inlet port 20 and a second end 58 bto be received in the second inlet port 22 to gradually increase ordecrease the flow of fluid as the needle valve is retracted from orinserted into each of the ports. The bimetal coil is oriented in thechamber and attached to the dual ended tapered needle valve to act onthe dual ended needle valve causing the respective ends to be insertedor retracted from each of the ports depending on the temperature of thefluid in the chamber, causing a restriction of flow in the second inletport, as shown in FIG. 5A, when the fluid in the chamber is below apredetermined lower threshold temperature or in the first inlet port, asshown in FIG. 5B, when the treatment fluid in the chamber is above apredetermined upper threshold temperature. As with the bimetal strip,winding and unwinding of the bimetal coil across the range from oneextremity of motion to the opposite extremity of motion reactive to thetemperatures between the high and low thresholds allows smooth controlof flow mixing between the first and second inlet ports.

In yet another alternative embodiment, as shown in FIG. 6A, thethermo-mechanical mixing valve is a pressure valve 18 c which employs asealed chamber 60, connected to the two inlet ports on opposite sides ofthe chamber and a thermo-mechanical actuation element 62 which isreactive providing expansion or contraction of a gas, liquid or gel thatis temperature sensitive contained in a vessel 64 supported within thechamber. A diaphragm (or piston) 66 is attached to a lever 68 which islaterally displaced by the fluid in actuation element 62 movingdiaphragm 66 between a first position substantially sealing the secondinlet port 22, shown in FIG. 6A, when the fluid in the chamber 60 isbelow a predetermined lower threshold temperature and to a secondposition substantially sealing the first inlet port 20, as shown in FIG.6B, when the treatment fluid in the chamber is above a predeterminedupper threshold temperature.

As with the bimetal mixing valves, greater control of flow can beachieved with the pressure valve as shown in FIG. 7A where a dual endedtapered needle valve 70 is connected to the lever 68 and adapted for afirst end 72 a to be received in in the first inlet port 20 and a secondend 72 b to be received in the second inlet port 22 to graduallyincrease or decrease the flow of fluid as the needle valve is retractedfrom or inserted into each of the ports. The lever 68 is oriented in thechamber and attached to the dual ended tapered needle valve to act onthe dual ended needle valve causing the respective ends to be insertedor retracted from each of the ports depending on the temperature of thefluid in the chamber, causing a restriction of flow in the second inletport, as shown in FIG. 7A, when the fluid in the chamber is below apredetermined lower threshold temperature or in the first inlet port, asshown in FIG. 5B, when the treatment fluid in the chamber is above apredetermined upper threshold temperature. As with the bimetal mixingvalves, expansion and contraction of the fluid contained in theactuation element 62 across the range from full contraction to fullexpansion reactive to the temperatures between the high and lowthresholds allows smooth control of flow mixing between the first andsecond inlet ports.

The embodiments disclosed herein allow a method for operation of a coldtherapy pad as shown in FIG. 8. A reservoir is provided containing acold treatment fluid, step 802, and a treatment pad is provided with aninlet line and an outlet line, step 804. A thermo-mechanical mixingvalve receives cold treatment fluid from the reservoir through a firstport, step 806, and fluid from the pad outlet line through a secondport, step 808. The thermo-mechanical mixing valve is reactiveresponsive to temperature to mix fluid from the reservoir and fluid fromthe pad outlet line in a ratio to provide fluid at a predeterminedtemperature to a valve outlet port, closing the first port responsive toa temperature below a lower threshold, step 810 and closing the secondport responsive to a temperature above an upper threshold, step 812. Thereaction of the thermo-mechanical mixing valve may be accomplished bybending of the bimetal strip, winding or unwinding of the bimetal coilor expanding or contracting a fluid in a sealed vessel in theembodiments as described. A pump is attached between the valve outletport and the pad inlet line, step 814, and a conduit is interconnectedbetween the pad outlet line and the reservoir, step 816.

Having now described various embodiments of the disclosure in detail asrequired by the patent statutes, those skilled in the art will recognizemodifications and substitutions to the specific embodiments disclosedherein. Such modifications are within the scope and intent of thepresent disclosure as defined in the following claims.

What is claimed is:
 1. A cold therapy unit comprising: a reservoircontaining a cold treatment fluid; a treatment pad with an inlet lineand an outlet line; a thermo-mechanical mixing valve receiving coldtreatment fluid from the reservoir through a first inlet port and fluidfrom the pad outlet line through a second inlet port, saidthermo-mechanical mixing valve reactive responsive to temperature to mixfluid from the reservoir and fluid from the pad outlet line in a ratioto provide fluid at a predetermined temperature to a valve outlet port;a pump attached to the valve outlet port and the pad inlet line todeliver the mixed treatment fluid from the mixing valve to the pad; anda conduit interconnecting the pad outlet line and the reservoir.
 2. Thecold therapy unit as defined in claim 1 further comprising a firstbifurcated line connected between the pad outlet line and the secondinlet port and a second bifurcated line as the conduit to recirculatewater to the reservoir as the conduit.
 3. The cold therapy unit asdefined in claim 1 wherein the reservoir comprises: a cold reservoirconnected to the first port; and, a holding reservoir connected to theconduit from the pad outlet line, said holding reservoir connected tothe second inlet port.
 4. The cold therapy unit as defined in claim 3wherein the cold reservoir and holding reservoir are interconnected witha leveling port.
 5. The cold therapy unit as defined in claim 1 whereinthe thermo-mechanical mixing valve comprises a bimetal mixing valve. 6.The cold therapy unit as defined in claim 5 wherein the bimetal mixingvalve comprises: a sealed chamber with the first and second inlet portson opposite sides of the chamber, the first inlet port receiving coldfluid from the reservoir and the second inlet port receiving warmerfluid from the outlet line of the treatment pad; and, a bimetal stripreactive by bending in accordance with exposure temperature is orientedin the chamber to block off the first inlet port when the temperature ofthe fluid in the chamber is below a predetermined lower threshold or thesecond inlet port when the treatment fluid in the chamber is above apredetermined upper threshold.
 7. The cold therapy unit as defined inclaim 6 further comprising adjustment screws engaged to the bimetalstrip to calibrate temperature at which the fluid in the chamber ismaintained.
 8. The cold therapy unit as defined in claim 6 furthercomprising: a dual ended tapered needle valve having a first endreceived in the first inlet port and a second end received in the secondinlet port, said first and second ends adapted to gradually increase ordecrease a flow of fluid associated inlet port as the needle valve isretracted from or inserted into each of the ports, said bimetal striporiented in the chamber to act on the dual ended needle valve causingthe respective ends to be inserted or retracted from the associatedports depending on the temperature of the fluid in the chamber causing arestriction of flow in the first inlet port when the fluid in thechamber is below a predetermined threshold temperature or in the secondinlet port when the treatment fluid in the chamber is above apredetermined threshold temperature.
 9. The cold therapy unit as definedin claim 5 wherein the bimetal mixing valve comprises: a sealed chamberwith first and second inlet ports on opposite sides of the chamber, thefirst inlet port receiving cold fluid from the reservoir and the secondinlet port receiving warmer fluid from the outlet line of the treatmentpad; a bimetal coil reactive by winding or unwinding in accordance withexposure temperature oriented in the chamber to block off the firstinlet port when the temperature of the fluid in the chamber is below apredetermined lower threshold or the second inlet port when thetreatment fluid in the chamber is above a predetermined upper threshold.10. The cold therapy unit as defined in claim 9 further comprising anadjustment screw at the center of the bimetal coil to calibratetemperature at which the fluid in the chamber is maintained.
 11. Thecold therapy unit as defined in claim 9 further comprising: a dual endedtapered needle valve having a first end received the first inlet portand a second end received in the second inlet port, said first andsecond ends adapted to gradually increase or decrease a flow of fluidassociated inlet port as the needle valve is retracted from or insertedinto each of the ports, said bimetal coil oriented in the chamber to acton the dual ended needle valve causing the respective ends to beinserted or retracted from the associated ports depending on thetemperature of the fluid in the chamber causing a restriction of flow inthe first inlet port when the fluid in the chamber is below apredetermined lower threshold temperature or in the second inlet portwhen the treatment fluid in the chamber is above a predetermined upperthreshold temperature.
 12. The cold therapy unit as defined in claim 1wherein the thermo-mechanical mixing valve comprises a pressure mixingvalve.
 13. The cold therapy unit as defined in claim 12 pressure mixingvalve comprises: a sealed chamber with first and second inlet ports onopposite sides of the chamber, the first inlet port receiving cold fluidfrom the reservoir and the second inlet port receiving warmer fluid fromthe outlet line of the treatment pad; a thermo-mechanical actuationelement reactive to temperature by providing expansion or contraction ofa fluid that is temperature sensitive contained in a vessel supportedwithin the chamber, a diaphragm is attached to a lever which islaterally displaced by the fluid in the actuation element moving thelever between a first position substantially sealing the second inletport when the fluid in the chamber is below a predetermined lowerthreshold temperature and to a second position substantially sealing thefirst inlet port when the treatment fluid in the chamber is above apredetermined upper threshold temperature.
 14. The cold therapy unit asdefined in claim 13 further comprising: a dual ended tapered needlevalve having a first end received the first inlet port and a second endreceived in the second inlet port, said first and second ends adapted togradually increase or decrease a flow of fluid associated inlet port asthe needle valve is retracted from or inserted into each of the ports,said lever oriented in the chamber to act on the dual ended needle valvecausing the respective ends to be inserted or retracted from theassociated ports depending on the temperature of the fluid in thechamber causing a restriction of flow in the first inlet port when thefluid in the chamber is below a predetermined lower thresholdtemperature or in the second inlet port when the treatment fluid in thechamber is above a predetermined upper threshold temperature.
 15. Amethod for providing cold therapy comprising: providing a reservoircontaining a cold treatment fluid; providing a treatment pad with aninlet line and an outlet line; connecting a bimetal mixing valve toreceives cold treatment fluid from the reservoir through a first portand fluid from the pad outlet line through a second port; closing thefirst port responsive to a temperature below a lower threshold byreaction of the thermo-mechanical mixing valve; closing the second portresponsive to a temperature above an upper threshold by reaction of thethermo-mechanical mixing valve; attaching a pump between an outlet porton the thermo-mechanical mixing valve and the pad inlet line; and,interconnecting a conduit between the pad outlet line and the reservoir.16. The method for providing cold therapy as defined in claim 15 whereinthe thermo-mechanical mixing valve incorporates a bimetal strip and saidreaction of the bimetal mixing valve comprises bending of the strip. 17.The method for providing cold therapy as defined in claim 15 wherein thethermo-mechanical mixing valve incorporates a bimetal coil and saidreaction of the thermo-mechanical mixing valve comprises winding orunwinding of the coil.
 18. The method for providing cold therapy asdefined in claim 15 wherein the thermo-mechanical mixing valveincorporates a fluid contained in a sealed vessel with a diaphragm orpiston and said reaction of the thermo-mechanical mixing valve comprisesthe expansion or contraction of said fluid causing said diaphragm orpiston to move out from or in towards said vessel.